Then you typed it wrong. If you're trying to give a player admin, type: /res pset PenguinDJ admin t Then click the green wool.
Still, do keep in mind that, depending on what you want to allow someone to do, you don't need to give them too many flags. For example: 'build' and 'chest' are enough to allow build & chest access. Optionally you can add the 'use' flag (opening doors and such) and perhaps 'redstone' to mess with redstone components if you use them. As others said; the problem with the admin flag is that you're basically making someone a co-owner of your residence. So they can do almost everything which you can do, including stuff such as resetting or unclaiming (which would reset the whole thing into its default state). (edited my post to avoid possible confusion, see next 2 messages)
That's invalid. Permissions such as /res reset; /res unclaim; /res default are reserved for residence owner only. Edit: Ninja'd by chickeneer
I stand corrected. Thanks for the update, I now wonder where I picked that information up. Even so; its good to know that admin does have its limits.